DRILLING OPERATIONS

FIELD OF THE INVENTION

[0001] The invention relates to a supervisory control system and method for automating drilling operations. More specifically, the invention relates to drilling control systems in which a supervisory controller controls one or more programmable logic controllers of a rig's control system, which in turn control rig and drilling equipment.

BACKGROUND OF THE INVENTION

[0002] Hydrocarbons obtained from subterranean formations are often used as energy resources, as feed stocks, and as consumer products. Concerns over depletion of available hydrocarbon resources and concerns over declining overall quality of produced

hydrocarbons have led to development of automated processes for more efficient drilling of oil and/or gas production wells, recovery, processing and/or use of available

hydrocarbon resources.

[0003] In drilling operations, drilling personnel are commonly assigned various monitoring and control functions. For example, drilling personnel may control or monitor positions of drilling apparatus (such as a rotary drive or carriage drive), collect samples of drilling fluid, and monitor shakers. As another example, drilling personnel adjust the drilling system on a case-by-case basis to adjust or correct drilling rate, trajectory, or stability. A driller may control drilling parameters using joysticks, manual switches, or other manually operated devices, and monitor drilling conditions using gauges, meters, dials, fluid samples, or audible alarms.

[0004] The need for manual (human) control and monitoring may increase costs of drilling of a formation. In addition, some of the operations performed by the driller may be based on subtle cues from drilling apparatus, such as unexpected noise or vibration of a drilling string. Because different drilling personnel have different experience, knowledge, skills, and instincts, drilling performance that relies on such manual procedures may not be repeatable from formation to formation or from rig to rig. In addition, some drilling operations may require that a drill bit be stopped or pulled off the bottom of the well, for example, when changing from a rotary drilling mode to a slide drilling mode. Suspension of drilling during such operations may reduce the overall rate of progress and efficiency of drilling. Bottom hole assemblies (BHA) in drilling systems often include instrumentation, such as Measurement While Drilling (MWD) tools. Data from the downhole

instrumentation may be used to monitor and control drilling operations. It may be difficult or impossible for a human operator to consistently and correctly assess or interpret the incoming data.

SUMMARY OF THE INVENTION

[0005] The invention provides an improved supervisory control system and method that enable automated supervisory control of complete drilling operations. The presence of automatic control systems allows the equipment status to be monitored consistently, MWD data to be consistently and correctly assessed, and optimized equipment control commands to be sent to the rig and downhole equipment.

[0006] In accordance with the invention, a supervisory control system for controlling a conventional drilling rig and drilling assembly while constructing a wellbore, in which the drilling rig comprising equipment includes a hoist-driven or hydraulic top drive system for providing axial and rotational movement to the drill string, a pumping system for drilling fluids, and an independent control system utilizing at least one Programmable Logic Controller (PLC) to convey operating instructions to the rig equipment, comprises a supervisory PLC in communication with the control system PLC(s), configured to perform a supervisory control function.

[0007] The supervisory control system may be constructed separately from the drilling rig and drilling assembly and/or may be retrofitted to a pre- existing drilling rig. The PLC and the at least one software application has the ability to use any of a series of standard industrial protocols for real time data exchange, including Modbus, Profibus, Profinet, OPC, WITS and WITSML and may also or alternatively include a series of individually developed interface protocols for each individual rig. The software application may further comprise a generic engineering unit system that can be adapted for each individual rig.

[0008] The invention further provides an information technology (IT) system as set out in detail below and a client workstation that can be remote from the hardware server, but is typically at the rig.

[0009] The present invention also provides a method for performing supervisory control of the operation of at least one drilling rig that includes at least one rig control PLC for the translation of control commands into instructions for rig and drilling equipment, comprising the steps of a) providing a supervisory PLC in communication with the rig control system PLC(s), and an information technology (IT) system, b) configuring the supervisory PLC to control a drilling operation, and c) controlling of a drilling operation by using the supervisory PLC to send control commands to the rig control PLC(s). Step a) may comprise adapting a generic engineering unit system for at least one drilling rig such that the configuration mirrors the specific engineering unit system of the rig under supervisory control, so that each data tag has the same value. Step c) may comprise executing an individually developed interface protocol for the at least one drilling rig, the interface including a mapping of tags of all data required on the rig control system to the same data on the supervisory control system, through which the data is transferred between the two systems in real time.

[0010] The supervisory PLC is preferably configured with software adapted to perform a supervisory control function such as supervisory control of drilling operations.

[0011] The supervisory PLC may be configured to execute automated supervisory control of all of the rig's main drilling and pipe handling equipment within a defined operating envelope that reflects the capacity limits of the equipment under control and the process limits of the process under control. In such a case, the defined operating envelope is respected via the utilization of a cause and effect matrix within the software logic, such that a breach of capacity limits or process limits or equipment zonal positioning laws will result in a defined response.

[0012] The supervisory PLC may also be configured to command the drilling rig equipment and drilling assembly to perform a sequence of activities including at least one of:

a. initialization of the rig equipment from a static state into an operating condition including, in any order;

i. acceleration and maintenance of the rate of fluid flow from the rig's mud flow system by increasing and maintaining the pump stroke rate of at least one of the rig's mud pumps;

ii. acceleration and maintenance of the rate of axial velocity of the rigs' top drive in the upward and downward directions by increasing and maintaining the rotational velocity of the rig's hoisting system or axial velocity of the hydraulic traveling block; and

iii. acceleration and maintenance of the rate of rotational velocity of the rig's rotary drive in the forward and reverse directions; recognizing steady state and recording tare value(s) at the appropriate time of at least one of load (WOB), pressure, and torque if rotating, wherein a tare value is defined as the value of a parameter measured after attainment of steady state of that parameter, and also one or more coexistent rig state parameter(s) defining valid drilling process circumstances, and assessing the validity of captured tare values by comparing to previous or predicted values, and comparing the deviation of the process value of each from its tare value against a set point for it while drilling;

running down by controlling the pumps, the hoist or hydraulic axial drive, and the rotary drive, wherein running down includes tagging the hole bottom and using sensing and interpretation to recognize and quantify compression of the drill string.

drilling, wherein drilling includes at least one of:

i. adaptive control of the rig equipment within the operating conditions, by applying defined sequences and interruptions to those sequences as per a cause-and-effect matrix;

ii. switching between drilling modes;

iii. selecting drilling modes based on requirements derived from a well position calculator;

iv. when rotary and / or slide drilling, applying an axial travel velocity limit;

v. using cascade control to limit axial travel based on the rate-of-change of any of the process values for which a tare has been taken and on a comparison of the value against a predefined set point for that value, such that the process parameter that has the lowest deviation of its process value from its set point is the active control parameter;

vi. in rotary and / or slide drilling mode, measuring the ratio of each of the tared process value deviation values to the rate of axial travel, and using the decline rate of those ratio values towards zero as an indication of formation hardness, and adjusting axial acceleration and deceleration based on them;

vii. in rotary or slide drilling modes, optimizing the set points of the cascade control system by increasing those set points in increments towards defined maximum limits, provided that no violations of selected cause and effect matrix occur within a defined sequence step;

viii. in rotary drilling mode, setting drill string RPM to a value calculated based on observation of other variables including wellbore position tendency and automatically adjusting it thereafter

ix. identification of undesired conditions during drilling including mud- motor stalling, bit and BHA hanging, stick-slip, bit and BHA whirl; x. mitigation of the identified undesired condition by responding via a cause and effect matrix that defines the required response based on the manner in which the undesired condition manifest over a defined interval of time

xi. when slide drilling, positioning the downhole mud motor toolface to a desired position while off bottom and while on bottom;

xii. providing at least two methods of maintaining orientation, selected from:

a. positional orientation consisting of projecting bit orientation using calculations of rate of change of the toolface from torque and WOB addition and release and axial travel;

b. deviation of string torque from an equilibrium condition of clockwise or counter-clockwise positive and negative torque applied to the drill string from the rig top drive system, and counter-clockwise torque applied to the drillstring from mud motor operations, wherein the equilibrium condition is held to maintain a toolface and a deviation from the equilibrium condition is applied to alter it;

c. use of a rotational rocking method including clockwise rotation to a limit, followed by counter-clockwise rotation to a limit to reduce the axial drag within the string, and applying toolface corrections as the equilibrium method above e. at the bottom of a joint of pipe or at the end of a defined sequence step, allowing the additional load compressed into the length of the drill string to drill-off, and recording the rate at which the process variables for the cascade controllers decline towards zero as further input towards adjusting axial acceleration and deceleration;

f. picking up the drill string from the on-bottom condition to an off-bottom condition and using sensing and interpretation to recognize and quantify consequent elongation or shortening of the drill string;

g. reaming the drilled hole to condition it to a desired condition by axially reciprocating the drillstring while pumping and either rotating or not rotating, and using sensing and interpretation to determine the extent to which the hole is conditioned, and determining the stop requirement for the activity based on the hole condition assessment;

h. executing a coordinated shutdown of the rig equipment from an operating condition to a static state including, in any order:

i. deceleration of the rate axial velocity of the rigs' top drive in the upward and downward directions to a stop condition for the top drive by decreasing the rotational velocity of the rig's hoisting system or hydraulic traveling block axial velocity to a zero value; ii. deceleration of the rate of rotational velocity of the rig's rotary drive to a zero value

iii. deceleration of the rate of flow from the rig's mud flow system by decreasing the rate of pump stroking of each of the rig's pumps to zero values.

iv. automatically compensating controller tuning by observing process dynamics during the shutdown, or user tuning factors

[0013] The supervisory PLC may be further configured to command the pipe handling equipment of the rig to perform a sequence of activities in order to introduce a next joint of pipe for drilling, or to remove a pipe joint, including the execution of at least one of the following steps:

a) breaking-out of a connection of two joints of pipe connected together by instructing a make-up / break-out device to clamp around the pipe at the connection point and provide sufficient torque differential across the connection face that the connection comes free;

b) rotating the connection until it is free, including acceleration and maintenance of the rate of rotational velocity of the rig's rotary drive in the reverse direction;

c) advancing the top-drive from the position with the top drive pipe component at the connection in the upwards direction to a stopping position at which point there is sufficient vertical space to add another joint of pipe, including acceleration and maintenance of the rate of axial velocity of the rigs' top drive in the upward directions by increasing and maintaining the rotational velocity of the rig's hoisting system or axial velocity of the hydraulic traveling block;

d) instructing the rig's pipe handling equipment to locate, acquire and position a joint of pipe to or from a storage location from or to a location between the top drive and the top of the previous joint of pipe;

e) connecting the joint of pipe to both the previous joint of pipe and the top drive by, in any order;

i. advancing the top drive in the downwards direction from its previous stop position to a position wherein a connection can be made between the top drive and the joint of pipe;

ii. connecting the top drive to the top of the pipe by rotating the top drive pipe component until a required level of torque across the connection has been achieved;

iii. advancing the top drive in the downwards direction from its position at which its connection to the pipe has been made, to a position whereby a connection can be made between the bottom of the joint of pipe and the previous pipe; and

iv. connecting the bottom of the pipe to the top of the previous joint of pipe by rotating the top drive and the pipe until a required level of torque across the connection has been achieved;

f) making -up the connections of the joints between the top drive and the pipe, and the pipe and the previous pipe, by instructing a make-up / break-out device to clamp around the pipe and provide sufficient torque differential across the pipe connections faces that the connections achieve a predefined torque value g) resetting of the position of all pipe-handling equipment to a predefined location on the rig such that they will not interfere with the drilling sequence when re-commenced

[0014] The supervisory PLC may be configured to perform continuous sequences of introducing or removing joints of pipe to or from the drillstring such that the drillstring can be entered into or removed from the borehole in predefined multiple amounts of pipe up to a limit of the total amount of pipe required to extend from the bottom of the borehole to the top.

[0015] The supervisory PLC may also be adapted to accept input from an operator, said inputs are selected from the group consisting of changing set points, changing sequence commands, and changing the desired depth for switching drilling modes.

[0016] The supervisory PLC may have operations configurations installed using a batch sequence or "recipe" file generated off location and loaded to the site PLC using remote access IT infrastructure. Multiple supervisory PLCs may be configured in this way from a location remote from the supervisory PLCs

[0017] The supervisory PLC may be configured to generate performance metrics and calculate other process variables to assist with performance optimisation

[0018] As used in this specification and claims the following terms shall have the following meanings:

[0019] "Supervisory control" refers to control of a plurality of individual controllers or control loops, which in turn manipulate final control elements.

[0020] "SCADA system" refers to a Supervisory Control and Data Acquisition system.

[0021] "Above" and "below" refer to positions that are relatively closer to and farther from, respectively, the top of the borehole.

[0022] "Vertical" refers to the primary axis of the borehole above the device.

[0023] "Continuous" or "continuously" in the context of signals (such as magnetic, electromagnetic, voltage, or other electrical or magnetic signals) includes continuous signals and signals that are pulsed repeatedly over a selected period of time. Continuous signals may be sent or received at regular intervals or irregular intervals.

[0024] A "fluid" may be, but is not limited to, a gas, a liquid, an emulsion, a slurry, and/or a stream of solid particles that has flow characteristics similar to liquid flow.

[0025] "Fluid pressure" is a pressure generated by a fluid in a formation or a tubular or other pipework component. [0026] A "formation" includes one or more hydrocarbon containing layers, one or more non- hydrocarbon layers, an overburden, and/or an underburden.

[0027] "Hydrocarbon layers" refer to layers in the formation that contain hydrocarbons. The hydrocarbon layers may contain non- hydrocarbon material and hydrocarbon material.

[0028] The "overburden" and/or the "underburden" include one or more different types of impermeable materials. For example, the overburden and/or underburden may include rock, shale, mudstone, or wet/tight carbonate.

[0029] "Formation fluids" refer to fluids present in a formation and may include pyrolyzation fluid, synthesis gas, mobilized hydrocarbons, and water (steam). Formation fluids may include hydrocarbon fluids as well as non-hydrocarbon fluids.

[0030] "Produced fluids" refer to fluids removed from the formation.

[0031] "Thickness" of a layer refers to the thickness of a cross section of the layer, wherein the cross section is normal to a face of the layer.

[0032] "Wellbore" and "borehole" refer to a hole in a formation made by drilling or insertion of a conduit into the formation. As used herein, the terms "well" and "opening," when referring to an opening in the formation may be used interchangeably with the term "wellbore."

BRIEF DESCRIPTION OF THE DRAWING

[0033] For a more detailed understanding of the invention, reference is made to the accompanying drawing wherein Figure 1 illustrates a schematic diagram of a drilling system with a control system for performing drilling operations automatically according to one embodiment of the invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0034] Figure 1 shows a drilling system 100 for drilling an underground borehole in an earth formation 102. Drilling system 100 includes drilling platform 104, pump system 108, drill string 110, bottom hole assembly 112, and supervisory control system 114. Drill string 110 is preferably made of a series of drill pipes 116 that are sequentially added to drill string 110 as well 117 is drilled in formation 102, as is known in the art.

[0035] Drilling platform 104 includes a hoist-driven or hydraulic top drive 118, a rotary drive system 120, and a pipe handling system 122. Drilling platform 104 may be operated to drill well 117 and to advance drill string 110 and bottom hole assembly 112 into formation 104. An annular opening 126 may be formed between the exterior of drill string 110 and the sides of well 117. Casing 124 may be provided in well 117. Casing 124 may be provided over the entire length of well 117 or over a portion of well 117, as depicted in FIG. 1.

[0036] Bottom hole assembly 112 may include a drill collar 130, mud motor 132, drill bit 134, and measurement while drilling (MWD) tool 136. Drill bit 134 may be driven by mud motor 132. Mud motor 132 may be driven by a drilling fluid passed through the mud motor. The speed of drill bit 134 may be approximately proportional to the differential pressure across mud motor 132. As used herein, "differential pressure across a mud motor" may refer to the difference in pressure between fluid flowing into the mud motor and fluid flowing out of the mud motor. Drilling fluid may be referred to herein as "mud."

[0037] In some embodiments, drill bit 134 and/or mud motor 132 may be mounted on a bent sub of bottom hole assembly 112. As is known in the art, the bent sub may orient the drill bit at angle (off-axis) relative to the attitude of bottom hole assembly 112 and/or the end of drill string 110. A bent sub may be used, for example, for directional drilling of a well.

[0038] As is known in the art, each piece of equipment, including but not limited to pump system 108, top drive 118, rotary drive 120, and pipe handling system 122 may or may not be equipped with its own programmable logic controller (PLC) (not shown). Each equipment PLC forms part of an interconnected control loop that includes that PLC, a sensor, and the piece of equipment that is controlled by the PLC.

[0039] In preferred embodiments of the invention, some or all of the desired drilling operations are performed automatically. More specifically, supervisory control system 114 may be configured to perform the monitoring functions that would otherwise be assigned to a driller. Thus, supervisory control 114 is capable of controlling a conventional drilling rig and drilling assembly while constructing a wellbore.

[0040] Supervisory control system 114 preferably comprises a supervisory PLC that is in communication with each equipment PLC(s) so as to be able to control it. Supervisory control system 114 may be constructed separately from the drilling rig and drilling assembly and, in preferred embodiments may be retrofitted to the PLCs of a pre-existing drilling rig. In such cases, supervisory control system 114 may include a series of specifically-developed interface protocols for each individual rig. Supervisory control system 114 preferably has the ability to use any of a series of standard industrial protocols for real-time data exchange, including Modbus, Profibus, Profinet, OPC, WITS and WITSML and uses a generic engineering unit system that can be adapted for each individual rig.

[0041] In certain embodiments, drilling system 100 further includes an information technology (IT) system assembled from conventional components and comprising:

• a hardware server in communication with the supervisory PLC,

• at least one client workstation in communication with the hardware server,

• at least one switching and routing device configured to manage communication connections between the hardware server, the supervisory PLC and the at least one client workstation,

• at least one software server operating on the hardware server and configured to: o manage communications to the supervisory PLC,

o manage communications to client workstations,

o manage communications between itself and any other software servers, o host software applications,

o manage communications between software applications, o store data collected by the software applications,

• at least one software application running on the at least one software server, and the at least one client workstation, and configured to:

o communicate with the supervisory PLC,

o communicate between itself and any other required software

applications,

o execute functions and calculations,

o manage data flow and storage, and, optionally,

• an uninterruptable power supply (UPS) connected to the PLC, the hardware server and the at least one switch and routing device, and configured to provide continuous electrical power in the event of a mains power failure,

• a protective casing enclosing the PLC, the hardware server and the at least one switch and routing device.

[0042] Supervisory control system 114 is preferably configured to control a drilling operation at platform 104 by using the supervisory PLC to send control commands to the equipment PLC(s). If supervisory control system 114 is retrofitted to the rig, this may require executing a series of individually developed interface protocols for each individual rig, with each interface including a mapping of tags of all data required on the rig control system to the same data on the supervisory control system, through which the data is transferred between the two systems in real time. Likewise, configuring supervisory control system 114 to a particular rig may require adapting a generic engineering unit system for that rig, so that the configuration mirrors the specific engineering unit system of the rig under supervisory control, so that each data tag has the same value.

[0043] Supervisory control system 114 is preferably configured with software adapted to perform a supervisory control function, including supervisory control of drilling operations. More specifically, supervisory control system 114 is preferably configured to execute automated supervisory control of all of the rig's main drilling equipment within a defined operating envelope that reflects the capacity limits of the rig equipment under control, and the process limits of the process under control. In preferred embodiments, the defined operating envelope is respected via the utilization of a cause and effect matrix within the software logic, or lookup table, wherein a breach of capacity limits or process limits or equipment zonal positioning laws will result in defined responses up to and including discontinuation of supervisory control of the process under control

[0044] Supervisory control system 114 is preferably configured to command the drilling rig and drilling assembly to perform a sequence of activities that including at least one of: initialization of the drilling process after each new joint of pipe has been added, recording of tare values, running down of the drilling BHA from an elevated position to the bottom of the well, drilling, drill-off at the end of a length of pipe, picking up the BHA from the bottom of the well to an elevated position, reaming, shutdown of the drilling sequence in preparation for the addition of another joint of pipe, and addition of another joint of pipe.

[0045] In preferred embodiments, initialization of the rig includes coordinated

initialization of the rig equipment from a static state into an operating condition. More specifically, this entails acceleration and maintenance of the rate of fluid flow from pump system 108 by increasing and maintaining the pump stroke rate of at least one of the pumps, acceleration and maintenance of the rate of axial velocity of top drive 118 in the upward or downward direction by increasing and maintaining the rotational velocity of the hoisting system or axial velocity of the hydraulic traveling block, and acceleration and maintenance of the rate of rotational velocity of rotary drive 120 in the forward or reverse directions. [0046] The process of automatically recording tare values requires that the supervisory control system 114 recognize steady state of one or more variables and record a tare value(s) for that variable. Variables may include load (WOB and overpull), pressure, fluid flow rate into and out of the wellbore, viscous drag, and torque (if rotating). The controller' s definition of "steady state" may depend on the variables being tared. In rotary and/or slide drilling mode, the ratio of each of the tared process value deviation values to the rate of axial travel can be measured, and the decline rate of those ratio values towards zero can be used as an indication of formation hardness. Axial acceleration and deceleration can in turn be adjusted, based on this data. This process is sometimes referred to as auto-tuning.

[0047] The process of automatically controlling a running down sequence requires controlling pump system 108, top drive 118, and/or the slips and/or make-up equipment. In particular, it is desirable to control a running down sequence such that the bit reaches the hole bottom but does not impact it with undue force or begin drilling with excessive velocity. For long holes and holes with significant deviated or horizontal portions, this requires combining an estimation of the elasticity of the string with sensing and interpretation.

[0048] Once the bit is on bottom, supervisory control system 114 is preferably configured to commence drilling. Automatic control of the drilling operation requires controlling pump system 108, top drive 118, and rotary drive 120. Automatic control of the drilling operation may further require adaptive control of the rig equipment within the desired operating conditions.

[0049] In some embodiments, supervisory control system 114 may drill in either rotary or slide drilling mode and may switch between rotary drilling and slide drilling. In rotary drilling, the rate of penetration (ROP), mechanical specific energy (MSE), or other desired parameter may be determined or optimized according to the algorithms set out in PCT application PCT/US2013/062211, filed on 27 September 2013 and entitled "Methods For Continual Refinement Of Operating Parameters." In some embodiments, the selection of drilling modes may be based on requirements derived from a well position calculator, such as is disclosed in PCT application WO2011130159.

[0050] In slide drilling, supervisory control system 114 may be configured to maneuver a downhole motor orientation (toolface) to a desired position while off bottom or on bottom. The desired orientation may be maintained by one or more known techniques, including using positional calculations, i.e. projecting where the toolface is using calculations of differential pressure, torque, and walk rate of the toolface when it is moving using the balance of torque in the string from surface rotary movements and reactive torque from mud motor when drilling , using drag-reduction techniques such as pipe-rocking and biasing the toolface by applying additional force on any single rocking movement, and/or by using a biasing technique such as the technique disclosed in US patent 7588100.

[0051] In preferred embodiments, the present automatic control of a drilling operation may further include the capabilities of recognition and mitigation of non-optimal drilling conditions such as mud motor stall, BHA hanging and BHA vibration modes (such as stick-slip and whirl). The supervisory control system 114 preferably includes subroutines that are run in each instance and send commands to pump system 108, top drive 118, and/or rotary drive 120 that mitigate or eliminate the undesirable situation.

[0052] During drilling, the present system is preferably configured to use a cascade control protocol in which supervisory controller 114 controls the top drive 118 so as to limit the axial velocity of the top drive and in turn, drill bit ROP. Specifically, differential values of measured pressure, torque and load while drilling from their non-drilling tare values are used in a cascade manner wherein the lowest delta value of the measured differential value to a desired set point value is used to select that controller as the current controller that limits top drive velocity. If the present system is drilling and encounters a limit of a controlled or measured value as defined in the cause and effect matrix, an interlock is enabled to limit up to and including all elements of further activity until the condition is cleared.

[0053] In rotary or slide drilling modes, the set points of the cascade control system may be optimized by increasing those set points in increments towards defined maximum limits, provided that no violations of selected cause and effect matrix occur within a defined sequence step.

[0054] In preferred embodiments, the present automatic control of the drilling operation may further include the application of a calculated time constant for each of the differential values of measured pressure, torque and load to determine the rate at which the drilling string compresses or decompresses when being placed onto or lifted from the bottom of the well, from which process gain values are then determined for each differential value. In one embodiment, the time constant can be calculated according to:

wherein WOB is defined as weight acting on a drill bit disposed on said drill assembly, ROP is defined as the rate at which said drill assembly penetrates a drill site, L is defined as the length of a drill pipe defined by said drill assembly, E is defined as the modulus of elasticity of material comprising a drill pipe disposed on said drill assembly, and A is defined as the cross sectional area of said drill pipe.

[0055] These process gain values can be used in the tuning of the Proportional and Integral elements of a regular PID control loop, which controls the rate of acceleration of the top drive axial velocity from a current speed setting to a desired speed setting.

[0056] It is also possible to transition between slide or rotary drilling modes, by sending sequenced commands to the controller to pick the drill bit up from the bottom of the hole and adjust the rotational velocity, orient the toolface to the desired setting in slide mode, and return the drill bit to the bottom of the hole and recommence drilling

[0057] Once the bit has reached a desired depth or end of the current length of pipe, drilling ceases. At this point, it may be desirable to backream the recently-drilled portion of the hole. This entails picking up the bit while it is rotating. In rotary drilling, these three controllers limit overpull, whereas in slide drilling only ΔΡ and AL controllers limit overpull.

[0058] The system is preferably configured to receive one or more inputs relating to the desired processes, process parameters, and decision criteria, to select a sequence of activities based on those inputs, and to establish control logic that reflects the inputs. By way of example, the supervisory PLC can accept inputs changing set points or changing sequence commands (including depth for switching drilling modes). The PLC is preferably configured to execute sequences of the control behaviour, within the defined operating envelope(s) as per the desired inputs. This may include performing complex calculations of engineering parameters in real time and display the results, if desired, and responding the supervisory control commands to those results; including slide drilling commands, open hole friction factor, and wellbore cleaning index

[0059] The present system is preferably also adapted to control a coordinated shutdown of the rig equipment from an operating condition to a static state. [0060] In certain embodiments, the supervisory control system may be adapted to control pipe-handling equipment (including the top drive, and, optionally, queuing systems) in response to input from a pipe-handling PLC. The pipe-handling PLC itself may also be a supervisory PLC and it may be configured to control connection sequences and tripping sequences.

[0061] Those of skill in the art will appreciate that many modifications and variations are possible of the disclosed embodiments, configurations, materials, and methods described and depicted herein. Accordingly, the claims and their functional equivalents should not be limited by the particular embodiments described and illustrated, as these are merely exemplary in nature and elements described separately may be optionally combined.